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December 27, 2009

Pesticides and Autism

Women who live near California farm fields sprayed with organochlorine pesticides may be more likely to give birth to children with autism, according to a study by state health officials to be published today.

The rate of autism among the children of 29 women who lived near the fields was extremely high, suggesting that exposure to the insecticides in the womb might have played a role. The study shows a link between pesticides and the neurological disorder, which affects one in every 150 children.
Examining three years of birth records and pesticide data, scientists from the Public Health Department determined that the Central Valley women lived within 500 meters (547 yards) of fields sprayed with organochlorine pesticides during their first trimester of pregnancy. Eight of them, or 28%, had children with autism. Their rate of autism was six times greater than for mothers who did not live near the fields. [Compare with national US prevalence rates for children born in 1998.]

Susan Kegley, senior scientist of Pesticide Action Network North America, a San Francisco-based advocacy group, said the report adds to an existing body of evidence that endosulfan and dicofol, already banned in some countries, are harmful.

For most pesticides, no unusual numbers of autism cases were found, but the exception was a class of compounds called organochlorines. Most, including DDT, were banned in the United States several decades ago because they were building up in the environment. Only dicofol and endosulfan remain.

Both affect nerves and the brain -- and cause reproductive effects and alter hormones in animal tests.

Organochlorine pesticides are mostly used as insecticides, from pellet application in field crops, to sprays for seed coating and grain storage. Some organochlorines are applied to surfaces to kill insects that land there, for example, the spraying of interior home walls with DDT to control mosquitos and the malaria they carry. Other organochlorines - such as chlordane, heptachlor and pentachlorophenol - are used to treat wood to prevent pest damage.

Endosulfan is still in widespread use in the U.S. to control pests in vegetables, fruits, cereal grains, and cotton, as well as ornamental shrubs, trees, vines, and ornamental plants. Internationally, its use in African cotton production is common, and it is applied to control pests on cashew plantations in India.

Lindane has been used to protect crop seeds from insects, for pest control in forests, on livestock and household pets for control of ticks and other pests, and in homes to control ants and other household pests. It is also the active ingredient in many medicated shampoos and soaps to control head lice and scabies.

Pesticide residues on food are a major source of organochlorine exposure. Organochlorines are some of the chemicals found most often in blood, adipose tissue (body fat) and breastmilk. Because of their chemical structure, organochlorines break down slowly, build up in fatty tissues, and remain in our bodies for a long time.

Organochlorines have a wide range of both acute and chronic health effects, including cancer, neurological damage, and birth defects. Many organochlorines are known hormone disruptors, and extremely low levels of exposure in the womb can cause irreversible damage to the reproductive and immune systems of the developing fetus.

A well-known organochlorine is DDT, which has been banned in many developed countries and dumped into third-world countries.

So, what of us poor sods in Malaysia where dangerous pesticides are technically banned, but with no enforcement?

Relatively high levels of pollution by organochlorines were found, particularly in Malaysia and the Philippines, compared to the other countries. In Malaysia, levels of aldrin and dieldrin in freshwater exceeded WHO Drinking Water Standards in some areas.

For DDT, DDE and DDD, US EPA Criteria for Human Consumption of Water and Organisms were frequently exceeded in a number of the [Asian] countries.

From a range of alkylphenols monitored by the laboratories, by far the highest results were for 4-nonylphenol. For most alkylphenols and Bisphenol A, comparatively higher results were recorded from samples taken in coastal waters in Singapore.

Both Malaysia and the Philippines recorded levels of pentachlorophenol in excess of the US EPA Human Health Criteria for Consumption of Water and Organisms.

These are known hormone disruptors that cause neurological damage in children.

If it can increase the rates of autism by six, is it any wonder that rates of learning disabilities and ADHD have exploded as well?